using System;

using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Crypto.Utilities;

namespace Org.BouncyCastle.Crypto.Engines
{
	/**
	* an implementation of the AES (Rijndael), from FIPS-197.
	* <p>
	* For further details see: <a href="http://csrc.nist.gov/encryption/aes/">http://csrc.nist.gov/encryption/aes/</a>.
	*
	* This implementation is based on optimizations from Dr. Brian Gladman's paper and C code at
	* <a href="http://fp.gladman.plus.com/cryptography_technology/rijndael/">http://fp.gladman.plus.com/cryptography_technology/rijndael/</a>
	*
	* There are three levels of tradeoff of speed vs memory
	* Because java has no preprocessor, they are written as three separate classes from which to choose
	*
	* The fastest uses 8Kbytes of static tables to precompute round calculations, 4 256 word tables for encryption
	* and 4 for decryption.
	*
	* The middle performance version uses only one 256 word table for each, for a total of 2Kbytes,
	* adding 12 rotate operations per round to compute the values contained in the other tables from
	* the contents of the first.
	*
	* The slowest version uses no static tables at all and computes the values in each round.
	* </p>
	* <p>
	* This file contains the middle performance version with 2Kbytes of static tables for round precomputation.
	* </p>
	*/
	public class AesEngine
		: IBlockCipher
	{
		// The S box
		private static readonly byte[] S =
		{
			99,	124, 119, 123, 242, 107, 111, 197,
			48, 1, 103, 43, 254, 215, 171, 118,
			202, 130, 201, 125, 250, 89, 71, 240,
			173, 212, 162, 175, 156, 164, 114, 192,
			183, 253, 147, 38, 54, 63, 247, 204,
			52, 165, 229, 241, 113, 216, 49, 21,
			4, 199, 35, 195, 24, 150, 5, 154,
			7, 18, 128, 226, 235, 39, 178, 117,
			9, 131, 44, 26, 27, 110, 90, 160,
			82, 59, 214, 179, 41, 227, 47, 132,
			83, 209, 0, 237, 32, 252, 177, 91,
			106, 203, 190, 57, 74, 76, 88, 207,
			208, 239, 170, 251, 67, 77, 51, 133,
			69, 249, 2, 127, 80, 60, 159, 168,
			81, 163, 64, 143, 146, 157, 56, 245,
			188, 182, 218, 33, 16, 255, 243, 210,
			205, 12, 19, 236, 95, 151, 68, 23,
			196, 167, 126, 61, 100, 93, 25, 115,
			96, 129, 79, 220, 34, 42, 144, 136,
			70, 238, 184, 20, 222, 94, 11, 219,
			224, 50, 58, 10, 73, 6, 36, 92,
			194, 211, 172, 98, 145, 149, 228, 121,
			231, 200, 55, 109, 141, 213, 78, 169,
			108, 86, 244, 234, 101, 122, 174, 8,
			186, 120, 37, 46, 28, 166, 180, 198,
			232, 221, 116, 31, 75, 189, 139, 138,
			112, 62, 181, 102, 72, 3, 246, 14,
			97, 53, 87, 185, 134, 193, 29, 158,
			225, 248, 152, 17, 105, 217, 142, 148,
			155, 30, 135, 233, 206, 85, 40, 223,
			140, 161, 137, 13, 191, 230, 66, 104,
			65, 153, 45, 15, 176, 84, 187, 22,
		};

		// The inverse S-box
		private static readonly byte[] Si =
		{
			82, 9, 106, 213, 48, 54, 165, 56,
			191, 64, 163, 158, 129, 243, 215, 251,
			124, 227, 57, 130, 155, 47, 255, 135,
			52, 142, 67, 68, 196, 222, 233, 203,
			84, 123, 148, 50, 166, 194, 35, 61,
			238, 76, 149, 11, 66, 250, 195, 78,
			8, 46, 161, 102, 40, 217, 36, 178,
			118, 91, 162, 73, 109, 139, 209, 37,
			114, 248, 246, 100, 134, 104, 152, 22,
			212, 164, 92, 204, 93, 101, 182, 146,
			108, 112, 72, 80, 253, 237, 185, 218,
			94, 21, 70, 87, 167, 141, 157, 132,
			144, 216, 171, 0, 140, 188, 211, 10,
			247, 228, 88, 5, 184, 179, 69, 6,
			208, 44, 30, 143, 202, 63, 15, 2,
			193, 175, 189, 3, 1, 19, 138, 107,
			58, 145, 17, 65, 79, 103, 220, 234,
			151, 242, 207, 206, 240, 180, 230, 115,
			150, 172, 116, 34, 231, 173, 53, 133,
			226, 249, 55, 232, 28, 117, 223, 110,
			71, 241, 26, 113, 29, 41, 197, 137,
			111, 183, 98, 14, 170, 24, 190, 27,
			252, 86, 62, 75, 198, 210, 121, 32,
			154, 219, 192, 254, 120, 205, 90, 244,
			31, 221, 168, 51, 136, 7, 199, 49,
			177, 18, 16, 89, 39, 128, 236, 95,
			96, 81, 127, 169, 25, 181, 74, 13,
			45, 229, 122, 159, 147, 201, 156, 239,
			160, 224, 59, 77, 174, 42, 245, 176,
			200, 235, 187, 60, 131, 83, 153, 97,
			23, 43, 4, 126, 186, 119, 214, 38,
			225, 105, 20, 99, 85, 33, 12, 125,
		};

		// vector used in calculating key schedule (powers of x in GF(256))
		private static readonly byte[] rcon =
		{
			0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36, 0x6c, 0xd8, 0xab, 0x4d, 0x9a,
			0x2f, 0x5e, 0xbc, 0x63, 0xc6, 0x97, 0x35, 0x6a, 0xd4, 0xb3, 0x7d, 0xfa, 0xef, 0xc5, 0x91
		};

		// precomputation tables of calculations for rounds
		private static readonly uint[] T0 =
		{
			0xa56363c6, 0x847c7cf8, 0x997777ee, 0x8d7b7bf6, 0x0df2f2ff,
			0xbd6b6bd6, 0xb16f6fde, 0x54c5c591, 0x50303060, 0x03010102,
			0xa96767ce, 0x7d2b2b56, 0x19fefee7, 0x62d7d7b5, 0xe6abab4d,
			0x9a7676ec, 0x45caca8f, 0x9d82821f, 0x40c9c989, 0x877d7dfa,
			0x15fafaef, 0xeb5959b2, 0xc947478e, 0x0bf0f0fb, 0xecadad41,
			0x67d4d4b3, 0xfda2a25f, 0xeaafaf45, 0xbf9c9c23, 0xf7a4a453,
			0x967272e4, 0x5bc0c09b, 0xc2b7b775, 0x1cfdfde1, 0xae93933d,
			0x6a26264c, 0x5a36366c, 0x413f3f7e, 0x02f7f7f5, 0x4fcccc83,
			0x5c343468, 0xf4a5a551, 0x34e5e5d1, 0x08f1f1f9, 0x937171e2,
			0x73d8d8ab, 0x53313162, 0x3f15152a, 0x0c040408, 0x52c7c795,
			0x65232346, 0x5ec3c39d, 0x28181830, 0xa1969637, 0x0f05050a,
			0xb59a9a2f, 0x0907070e, 0x36121224, 0x9b80801b, 0x3de2e2df,
			0x26ebebcd, 0x6927274e, 0xcdb2b27f, 0x9f7575ea, 0x1b090912,
			0x9e83831d, 0x742c2c58, 0x2e1a1a34, 0x2d1b1b36, 0xb26e6edc,
			0xee5a5ab4, 0xfba0a05b, 0xf65252a4, 0x4d3b3b76, 0x61d6d6b7,
			0xceb3b37d, 0x7b292952, 0x3ee3e3dd, 0x712f2f5e, 0x97848413,
			0xf55353a6, 0x68d1d1b9, 0x00000000, 0x2cededc1, 0x60202040,
			0x1ffcfce3, 0xc8b1b179, 0xed5b5bb6, 0xbe6a6ad4, 0x46cbcb8d,
			0xd9bebe67, 0x4b393972, 0xde4a4a94, 0xd44c4c98, 0xe85858b0,
			0x4acfcf85, 0x6bd0d0bb, 0x2aefefc5, 0xe5aaaa4f, 0x16fbfbed,
			0xc5434386, 0xd74d4d9a, 0x55333366, 0x94858511, 0xcf45458a,
			0x10f9f9e9, 0x06020204, 0x817f7ffe, 0xf05050a0, 0x443c3c78,
			0xba9f9f25, 0xe3a8a84b, 0xf35151a2, 0xfea3a35d, 0xc0404080,
			0x8a8f8f05, 0xad92923f, 0xbc9d9d21, 0x48383870, 0x04f5f5f1,
			0xdfbcbc63, 0xc1b6b677, 0x75dadaaf, 0x63212142, 0x30101020,
			0x1affffe5, 0x0ef3f3fd, 0x6dd2d2bf, 0x4ccdcd81, 0x140c0c18,
			0x35131326, 0x2fececc3, 0xe15f5fbe, 0xa2979735, 0xcc444488,
			0x3917172e, 0x57c4c493, 0xf2a7a755, 0x827e7efc, 0x473d3d7a,
			0xac6464c8, 0xe75d5dba, 0x2b191932, 0x957373e6, 0xa06060c0,
			0x98818119, 0xd14f4f9e, 0x7fdcdca3, 0x66222244, 0x7e2a2a54,
			0xab90903b, 0x8388880b, 0xca46468c, 0x29eeeec7, 0xd3b8b86b,
			0x3c141428, 0x79dedea7, 0xe25e5ebc, 0x1d0b0b16, 0x76dbdbad,
			0x3be0e0db, 0x56323264, 0x4e3a3a74, 0x1e0a0a14, 0xdb494992,
			0x0a06060c, 0x6c242448, 0xe45c5cb8, 0x5dc2c29f, 0x6ed3d3bd,
			0xefacac43, 0xa66262c4, 0xa8919139, 0xa4959531, 0x37e4e4d3,
			0x8b7979f2, 0x32e7e7d5, 0x43c8c88b, 0x5937376e, 0xb76d6dda,
			0x8c8d8d01, 0x64d5d5b1, 0xd24e4e9c, 0xe0a9a949, 0xb46c6cd8,
			0xfa5656ac, 0x07f4f4f3, 0x25eaeacf, 0xaf6565ca, 0x8e7a7af4,
			0xe9aeae47, 0x18080810, 0xd5baba6f, 0x887878f0, 0x6f25254a,
			0x722e2e5c, 0x241c1c38, 0xf1a6a657, 0xc7b4b473, 0x51c6c697,
			0x23e8e8cb, 0x7cdddda1, 0x9c7474e8, 0x211f1f3e, 0xdd4b4b96,
			0xdcbdbd61, 0x868b8b0d, 0x858a8a0f, 0x907070e0, 0x423e3e7c,
			0xc4b5b571, 0xaa6666cc, 0xd8484890, 0x05030306, 0x01f6f6f7,
			0x120e0e1c, 0xa36161c2, 0x5f35356a, 0xf95757ae, 0xd0b9b969,
			0x91868617, 0x58c1c199, 0x271d1d3a, 0xb99e9e27, 0x38e1e1d9,
			0x13f8f8eb, 0xb398982b, 0x33111122, 0xbb6969d2, 0x70d9d9a9,
			0x898e8e07, 0xa7949433, 0xb69b9b2d, 0x221e1e3c, 0x92878715,
			0x20e9e9c9, 0x49cece87, 0xff5555aa, 0x78282850, 0x7adfdfa5,
			0x8f8c8c03, 0xf8a1a159, 0x80898909, 0x170d0d1a, 0xdabfbf65,
			0x31e6e6d7, 0xc6424284, 0xb86868d0, 0xc3414182, 0xb0999929,
			0x772d2d5a, 0x110f0f1e, 0xcbb0b07b, 0xfc5454a8, 0xd6bbbb6d,
			0x3a16162c
		};

		private static readonly uint[] Tinv0 =
		{
			0x50a7f451, 0x5365417e, 0xc3a4171a, 0x965e273a, 0xcb6bab3b,
			0xf1459d1f, 0xab58faac, 0x9303e34b, 0x55fa3020, 0xf66d76ad,
			0x9176cc88, 0x254c02f5, 0xfcd7e54f, 0xd7cb2ac5, 0x80443526,
			0x8fa362b5, 0x495ab1de, 0x671bba25, 0x980eea45, 0xe1c0fe5d,
			0x02752fc3, 0x12f04c81, 0xa397468d, 0xc6f9d36b, 0xe75f8f03,
			0x959c9215, 0xeb7a6dbf, 0xda595295, 0x2d83bed4, 0xd3217458,
			0x2969e049, 0x44c8c98e, 0x6a89c275, 0x78798ef4, 0x6b3e5899,
			0xdd71b927, 0xb64fe1be, 0x17ad88f0, 0x66ac20c9, 0xb43ace7d,
			0x184adf63, 0x82311ae5, 0x60335197, 0x457f5362, 0xe07764b1,
			0x84ae6bbb, 0x1ca081fe, 0x942b08f9, 0x58684870, 0x19fd458f,
			0x876cde94, 0xb7f87b52, 0x23d373ab, 0xe2024b72, 0x578f1fe3,
			0x2aab5566, 0x0728ebb2, 0x03c2b52f, 0x9a7bc586, 0xa50837d3,
			0xf2872830, 0xb2a5bf23, 0xba6a0302, 0x5c8216ed, 0x2b1ccf8a,
			0x92b479a7, 0xf0f207f3, 0xa1e2694e, 0xcdf4da65, 0xd5be0506,
			0x1f6234d1, 0x8afea6c4, 0x9d532e34, 0xa055f3a2, 0x32e18a05,
			0x75ebf6a4, 0x39ec830b, 0xaaef6040, 0x069f715e, 0x51106ebd,
			0xf98a213e, 0x3d06dd96, 0xae053edd, 0x46bde64d, 0xb58d5491,
			0x055dc471, 0x6fd40604, 0xff155060, 0x24fb9819, 0x97e9bdd6,
			0xcc434089, 0x779ed967, 0xbd42e8b0, 0x888b8907, 0x385b19e7,
			0xdbeec879, 0x470a7ca1, 0xe90f427c, 0xc91e84f8, 0x00000000,
			0x83868009, 0x48ed2b32, 0xac70111e, 0x4e725a6c, 0xfbff0efd,
			0x5638850f, 0x1ed5ae3d, 0x27392d36, 0x64d90f0a, 0x21a65c68,
			0xd1545b9b, 0x3a2e3624, 0xb1670a0c, 0x0fe75793, 0xd296eeb4,
			0x9e919b1b, 0x4fc5c080, 0xa220dc61, 0x694b775a, 0x161a121c,
			0x0aba93e2, 0xe52aa0c0, 0x43e0223c, 0x1d171b12, 0x0b0d090e,
			0xadc78bf2, 0xb9a8b62d, 0xc8a91e14, 0x8519f157, 0x4c0775af,
			0xbbdd99ee, 0xfd607fa3, 0x9f2601f7, 0xbcf5725c, 0xc53b6644,
			0x347efb5b, 0x7629438b, 0xdcc623cb, 0x68fcedb6, 0x63f1e4b8,
			0xcadc31d7, 0x10856342, 0x40229713, 0x2011c684, 0x7d244a85,
			0xf83dbbd2, 0x1132f9ae, 0x6da129c7, 0x4b2f9e1d, 0xf330b2dc,
			0xec52860d, 0xd0e3c177, 0x6c16b32b, 0x99b970a9, 0xfa489411,
			0x2264e947, 0xc48cfca8, 0x1a3ff0a0, 0xd82c7d56, 0xef903322,
			0xc74e4987, 0xc1d138d9, 0xfea2ca8c, 0x360bd498, 0xcf81f5a6,
			0x28de7aa5, 0x268eb7da, 0xa4bfad3f, 0xe49d3a2c, 0x0d927850,
			0x9bcc5f6a, 0x62467e54, 0xc2138df6, 0xe8b8d890, 0x5ef7392e,
			0xf5afc382, 0xbe805d9f, 0x7c93d069, 0xa92dd56f, 0xb31225cf,
			0x3b99acc8, 0xa77d1810, 0x6e639ce8, 0x7bbb3bdb, 0x097826cd,
			0xf418596e, 0x01b79aec, 0xa89a4f83, 0x656e95e6, 0x7ee6ffaa,
			0x08cfbc21, 0xe6e815ef, 0xd99be7ba, 0xce366f4a, 0xd4099fea,
			0xd67cb029, 0xafb2a431, 0x31233f2a, 0x3094a5c6, 0xc066a235,
			0x37bc4e74, 0xa6ca82fc, 0xb0d090e0, 0x15d8a733, 0x4a9804f1,
			0xf7daec41, 0x0e50cd7f, 0x2ff69117, 0x8dd64d76, 0x4db0ef43,
			0x544daacc, 0xdf0496e4, 0xe3b5d19e, 0x1b886a4c, 0xb81f2cc1,
			0x7f516546, 0x04ea5e9d, 0x5d358c01, 0x737487fa, 0x2e410bfb,
			0x5a1d67b3, 0x52d2db92, 0x335610e9, 0x1347d66d, 0x8c61d79a,
			0x7a0ca137, 0x8e14f859, 0x893c13eb, 0xee27a9ce, 0x35c961b7,
			0xede51ce1, 0x3cb1477a, 0x59dfd29c, 0x3f73f255, 0x79ce1418,
			0xbf37c773, 0xeacdf753, 0x5baafd5f, 0x146f3ddf, 0x86db4478,
			0x81f3afca, 0x3ec468b9, 0x2c342438, 0x5f40a3c2, 0x72c31d16,
			0x0c25e2bc, 0x8b493c28, 0x41950dff, 0x7101a839, 0xdeb30c08,
			0x9ce4b4d8, 0x90c15664, 0x6184cb7b, 0x70b632d5, 0x745c6c48,
			0x4257b8d0
		};

		private uint Shift(
			uint	r,
			int		shift)
		{
			return (r >> shift) | (r << (32 - shift));
		}

		/* multiply four bytes in GF(2^8) by 'x' {02} in parallel */

		private const uint m1 = 0x80808080;
		private const uint m2 = 0x7f7f7f7f;
		private const uint m3 = 0x0000001b;

		private uint FFmulX(
			uint x)
		{
			return ((x & m2) << 1) ^ (((x & m1) >> 7) * m3);
		}

		/*
		The following defines provide alternative definitions of FFmulX that might
		give improved performance if a fast 32-bit multiply is not available.

		private int FFmulX(int x) { int u = x & m1; u |= (u >> 1); return ((x & m2) << 1) ^ ((u >>> 3) | (u >>> 6)); }
		private static final int  m4 = 0x1b1b1b1b;
		private int FFmulX(int x) { int u = x & m1; return ((x & m2) << 1) ^ ((u - (u >>> 7)) & m4); }

		*/

		private uint Inv_Mcol(
			uint x)
		{
			uint f2 = FFmulX(x);
			uint f4 = FFmulX(f2);
			uint f8 = FFmulX(f4);
			uint f9 = x ^ f8;

			return f2 ^ f4 ^ f8 ^ Shift(f2 ^ f9, 8) ^ Shift(f4 ^ f9, 16) ^ Shift(f9, 24);
		}

		private uint SubWord(
			uint x)
		{
			return (uint)S[x&255]
				| (((uint)S[(x>>8)&255]) << 8)
				| (((uint)S[(x>>16)&255]) << 16)
				| (((uint)S[(x>>24)&255]) << 24);
		}

		/**
		* Calculate the necessary round keys
		* The number of calculations depends on key size and block size
		* AES specified a fixed block size of 128 bits and key sizes 128/192/256 bits
		* This code is written assuming those are the only possible values
		*/
		private uint[,] GenerateWorkingKey(
			byte[]	key,
			bool	forEncryption)
		{
			int KC = key.Length / 4;  // key length in words
			int t;

			if ((KC != 4) && (KC != 6) && (KC != 8)) 
				throw new ArgumentException("Key length not 128/192/256 bits.");

			ROUNDS = KC + 6;  // This is not always true for the generalized Rijndael that allows larger block sizes
			uint[,] W = new uint[ROUNDS+1, 4];   // 4 words in a block

			//
			// copy the key into the round key array
			//

			t = 0;
			for (int i = 0; i < key.Length; t++)
			{
				W[t >> 2, t & 3] = Pack.LE_To_UInt32(key, i);
				i+=4;
			}

			//
			// while not enough round key material calculated
			// calculate new values
			//
			int k = (ROUNDS + 1) << 2;
			for (int i = KC; (i < k); i++)
			{
				uint temp = W[(i-1)>>2, (i-1)&3];
				if ((i % KC) == 0) 
				{
					temp = SubWord(Shift(temp, 8)) ^ rcon[(i / KC)-1];
				} 
				else if ((KC > 6) && ((i % KC) == 4)) 
				{
					temp = SubWord(temp);
				}

				W[i>>2, i&3] = W[(i - KC)>>2, (i-KC)&3] ^ temp;
			}

			if (!forEncryption)
			{
				for (int j = 1; j < ROUNDS; j++)
				{
					for (int i = 0; i < 4; i++)
					{
						W[j, i] = Inv_Mcol(W[j, i]);
					}
				}
			}

			return W;
		}

		private int		ROUNDS;
		private uint[,]	WorkingKey;
		private uint	C0, C1, C2, C3;
		private bool	forEncryption;

		private const int BLOCK_SIZE = 16;

		/**
		* default constructor - 128 bit block size.
		*/
		public AesEngine()
		{
		}

		/**
		* initialise an AES cipher.
		*
		* @param forEncryption whether or not we are for encryption.
		* @param parameters the parameters required to set up the cipher.
		* @exception ArgumentException if the parameters argument is
		* inappropriate.
		*/
		public void Init(
			bool				forEncryption,
			ICipherParameters	parameters)
		{
			KeyParameter keyParameter = parameters as KeyParameter;

			if (keyParameter == null)
				throw new ArgumentException("invalid parameter passed to AES init - " + parameters.GetType().Name);

			WorkingKey = GenerateWorkingKey(keyParameter.GetKey(), forEncryption);

			this.forEncryption = forEncryption;
		}

		public string AlgorithmName
		{
			get { return "AES"; }
		}

		public bool IsPartialBlockOkay
		{
			get { return false; }
		}

		public int GetBlockSize()
		{
			return BLOCK_SIZE;
		}

		public int ProcessBlock(
			byte[]	input,
			int		inOff,
			byte[]	output,
			int		outOff)
		{
			if (WorkingKey == null)
			{
				throw new InvalidOperationException("AES engine not initialised");
			}

			if ((inOff + (32 / 2)) > input.Length)
			{
				throw new DataLengthException("input buffer too short");
			}

			if ((outOff + (32 / 2)) > output.Length)
			{
				throw new DataLengthException("output buffer too short");
			}

			UnPackBlock(input, inOff);

			if (forEncryption)
			{
				EncryptBlock(WorkingKey);
			}
			else
			{
				DecryptBlock(WorkingKey);
			}

			PackBlock(output, outOff);

			return BLOCK_SIZE;
		}

		public void Reset()
		{
		}

		private void UnPackBlock(
			byte[]	bytes,
			int		off)
		{
			C0 = Pack.LE_To_UInt32(bytes, off);
			C1 = Pack.LE_To_UInt32(bytes, off + 4);
			C2 = Pack.LE_To_UInt32(bytes, off + 8);
			C3 = Pack.LE_To_UInt32(bytes, off + 12);
		}

		private void PackBlock(
			byte[]	bytes,
			int		off)
		{
			Pack.UInt32_To_LE(C0, bytes, off);
			Pack.UInt32_To_LE(C1, bytes, off + 4);
			Pack.UInt32_To_LE(C2, bytes, off + 8);
			Pack.UInt32_To_LE(C3, bytes, off + 12);
		}

		private void EncryptBlock(
			uint[,] KW)
		{
			uint r, r0, r1, r2, r3;

			C0 ^= KW[0, 0];
			C1 ^= KW[0, 1];
			C2 ^= KW[0, 2];
			C3 ^= KW[0, 3];

			for (r = 1; r < ROUNDS - 1;)
			{
				r0 = T0[C0&255] ^ Shift(T0[(C1>>8)&255], 24) ^ Shift(T0[(C2>>16)&255],16) ^ Shift(T0[(C3>>24)&255],8) ^ KW[r,0];
				r1 = T0[C1&255] ^ Shift(T0[(C2>>8)&255], 24) ^ Shift(T0[(C3>>16)&255], 16) ^ Shift(T0[(C0>>24)&255], 8) ^ KW[r,1];
				r2 = T0[C2&255] ^ Shift(T0[(C3>>8)&255], 24) ^ Shift(T0[(C0>>16)&255], 16) ^ Shift(T0[(C1>>24)&255], 8) ^ KW[r,2];
				r3 = T0[C3&255] ^ Shift(T0[(C0>>8)&255], 24) ^ Shift(T0[(C1>>16)&255], 16) ^ Shift(T0[(C2>>24)&255], 8) ^ KW[r++,3];
				C0 = T0[r0&255] ^ Shift(T0[(r1>>8)&255], 24) ^ Shift(T0[(r2>>16)&255], 16) ^ Shift(T0[(r3>>24)&255], 8) ^ KW[r,0];
				C1 = T0[r1&255] ^ Shift(T0[(r2>>8)&255], 24) ^ Shift(T0[(r3>>16)&255], 16) ^ Shift(T0[(r0>>24)&255], 8) ^ KW[r,1];
				C2 = T0[r2&255] ^ Shift(T0[(r3>>8)&255], 24) ^ Shift(T0[(r0>>16)&255], 16) ^ Shift(T0[(r1>>24)&255], 8) ^ KW[r,2];
				C3 = T0[r3&255] ^ Shift(T0[(r0>>8)&255], 24) ^ Shift(T0[(r1>>16)&255], 16) ^ Shift(T0[(r2>>24)&255], 8) ^ KW[r++,3];
			}

			r0 = T0[C0&255] ^ Shift(T0[(C1>>8)&255], 24) ^ Shift(T0[(C2>>16)&255], 16) ^ Shift(T0[(C3>>24)&255], 8) ^ KW[r,0];
			r1 = T0[C1&255] ^ Shift(T0[(C2>>8)&255], 24) ^ Shift(T0[(C3>>16)&255], 16) ^ Shift(T0[(C0>>24)&255], 8) ^ KW[r,1];
			r2 = T0[C2&255] ^ Shift(T0[(C3>>8)&255], 24) ^ Shift(T0[(C0>>16)&255], 16) ^ Shift(T0[(C1>>24)&255], 8) ^ KW[r,2];
			r3 = T0[C3&255] ^ Shift(T0[(C0>>8)&255], 24) ^ Shift(T0[(C1>>16)&255], 16) ^ Shift(T0[(C2>>24)&255], 8) ^ KW[r++,3];

			// the final round's table is a simple function of S so we don't use a whole other four tables for it

			C0 = (uint)S[r0&255] ^ (((uint)S[(r1>>8)&255])<<8) ^ (((uint)S[(r2>>16)&255])<<16) ^ (((uint)S[(r3>>24)&255])<<24) ^ KW[r,0];
			C1 = (uint)S[r1&255] ^ (((uint)S[(r2>>8)&255])<<8) ^ (((uint)S[(r3>>16)&255])<<16) ^ (((uint)S[(r0>>24)&255])<<24) ^ KW[r,1];
			C2 = (uint)S[r2&255] ^ (((uint)S[(r3>>8)&255])<<8) ^ (((uint)S[(r0>>16)&255])<<16) ^ (((uint)S[(r1>>24)&255])<<24) ^ KW[r,2];
			C3 = (uint)S[r3&255] ^ (((uint)S[(r0>>8)&255])<<8) ^ (((uint)S[(r1>>16)&255])<<16) ^ (((uint)S[(r2>>24)&255])<<24) ^ KW[r,3];
		}

		private void DecryptBlock(
			uint[,] KW)
		{
			int r;
			uint r0, r1, r2, r3;

			C0 ^= KW[ROUNDS,0];
			C1 ^= KW[ROUNDS,1];
			C2 ^= KW[ROUNDS,2];
			C3 ^= KW[ROUNDS,3];

			for (r = ROUNDS-1; r>1;)
			{
				r0 = Tinv0[C0&255] ^ Shift(Tinv0[(C3>>8)&255], 24) ^ Shift(Tinv0[(C2>>16)&255], 16) ^ Shift(Tinv0[(C1>>24)&255], 8) ^ KW[r,0];
				r1 = Tinv0[C1&255] ^ Shift(Tinv0[(C0>>8)&255], 24) ^ Shift(Tinv0[(C3>>16)&255], 16) ^ Shift(Tinv0[(C2>>24)&255], 8) ^ KW[r,1];
				r2 = Tinv0[C2&255] ^ Shift(Tinv0[(C1>>8)&255], 24) ^ Shift(Tinv0[(C0>>16)&255], 16) ^ Shift(Tinv0[(C3>>24)&255], 8) ^ KW[r,2];
				r3 = Tinv0[C3&255] ^ Shift(Tinv0[(C2>>8)&255], 24) ^ Shift(Tinv0[(C1>>16)&255], 16) ^ Shift(Tinv0[(C0>>24)&255], 8) ^ KW[r--,3];
				C0 = Tinv0[r0&255] ^ Shift(Tinv0[(r3>>8)&255], 24) ^ Shift(Tinv0[(r2>>16)&255], 16) ^ Shift(Tinv0[(r1>>24)&255], 8) ^ KW[r,0];
				C1 = Tinv0[r1&255] ^ Shift(Tinv0[(r0>>8)&255], 24) ^ Shift(Tinv0[(r3>>16)&255], 16) ^ Shift(Tinv0[(r2>>24)&255], 8) ^ KW[r,1];
				C2 = Tinv0[r2&255] ^ Shift(Tinv0[(r1>>8)&255], 24) ^ Shift(Tinv0[(r0>>16)&255], 16) ^ Shift(Tinv0[(r3>>24)&255], 8) ^ KW[r,2];
				C3 = Tinv0[r3&255] ^ Shift(Tinv0[(r2>>8)&255], 24) ^ Shift(Tinv0[(r1>>16)&255], 16) ^ Shift(Tinv0[(r0>>24)&255], 8) ^ KW[r--,3];
			}

			r0 = Tinv0[C0&255] ^ Shift(Tinv0[(C3>>8)&255], 24) ^ Shift(Tinv0[(C2>>16)&255], 16) ^ Shift(Tinv0[(C1>>24)&255], 8) ^ KW[r,0];
			r1 = Tinv0[C1&255] ^ Shift(Tinv0[(C0>>8)&255], 24) ^ Shift(Tinv0[(C3>>16)&255], 16) ^ Shift(Tinv0[(C2>>24)&255], 8) ^ KW[r,1];
			r2 = Tinv0[C2&255] ^ Shift(Tinv0[(C1>>8)&255], 24) ^ Shift(Tinv0[(C0>>16)&255], 16) ^ Shift(Tinv0[(C3>>24)&255], 8) ^ KW[r,2];
			r3 = Tinv0[C3&255] ^ Shift(Tinv0[(C2>>8)&255], 24) ^ Shift(Tinv0[(C1>>16)&255], 16) ^ Shift(Tinv0[(C0>>24)&255], 8) ^ KW[r,3];

			// the final round's table is a simple function of Si so we don't use a whole other four tables for it

			C0 = (uint)Si[r0&255] ^ (((uint)Si[(r3>>8)&255])<<8) ^ (((uint)Si[(r2>>16)&255])<<16) ^ (((uint)Si[(r1>>24)&255])<<24) ^ KW[0,0];
			C1 = (uint)Si[r1&255] ^ (((uint)Si[(r0>>8)&255])<<8) ^ (((uint)Si[(r3>>16)&255])<<16) ^ (((uint)Si[(r2>>24)&255])<<24) ^ KW[0,1];
			C2 = (uint)Si[r2&255] ^ (((uint)Si[(r1>>8)&255])<<8) ^ (((uint)Si[(r0>>16)&255])<<16) ^ (((uint)Si[(r3>>24)&255])<<24) ^ KW[0,2];
			C3 = (uint)Si[r3&255] ^ (((uint)Si[(r2>>8)&255])<<8) ^ (((uint)Si[(r1>>16)&255])<<16) ^ (((uint)Si[(r0>>24)&255])<<24) ^ KW[0,3];
		}
	}
}
